Unemployment is stuck above 8%, the economy is slowing down and inflation hardly looks like a threat. So why did the Federal Reserve opt only to extend Operation Twist rather than launch a bold new program of bond buying in a third round of quantitative easing?

Blame it on the weather.

Yes, all the data point to a slowdown — from jobless claims and retail sales to regional manufacturing indexes and housing stats. But then we kind of knew this was coming.

Remember that stream of stronger-than-expected data we enjoyed during the first quarter? It was no secret that much if not most of it was given a big boost by surprisingly balmy winter weather. Indeed, thanks to mild temperatures, a great deal of economic activity, from housing starts and commercial construction to car sales and shopping, happened earlier this year than it otherwise would have.

At the same time, Fed Chairman Ben Bernanke & Co. have to drive forward while looking in the rearview mirror — and the data distortions make it harder than usual to see down the road.

So, although the backward-looking numbers do indeed look ugly, they could just be more evidence of the first quarter stealing from the second. And to confuse matters further, the leading indicators, which are just that — leading or forward looking, not backward looking — came in well ahead of expectations.

The bottom line is that the economy and the jobs picture have deteriorated, but given how much unseasonable conditions messed with the numbers, no one really knows whether it’s a temporary setback or the beginning of a scary new trend. And what’s going on in Europe only complicates matters even more.

Now, consider that economists’ track record as a whole is pretty bad when it comes to predicting, well, everything. The Fed is no exception. Bernanke doesn’t have a crystal ball. And so, under the circumstances, the Fed yesterday did the minimum it could do under the circumstances, says David Rosenberg, chief economist and strategist at Gluskin Sheff.

“The bottom line is that the Fed has been all over the map with respect to its periodic forecasting and likely did not want to be seen as over-reacting, especially since policymakers don’t yet have a grasp on whether the recent weakness in data has been exaggerated by the weather-related boost we enjoyed during the winter,” Rosenberg wrote in Thursday report to clients.

Indeed, it’s possible that launching a third round of quantitative easing could have been misinterpreted as the Fed shrieking that the sky is falling.

When it comes to the future course of the economy, it’s simply still way too soon to tell. As bad as things appear, they’re not definitively getting bad enough to warrant QE3 just yet. And since the situation could deteriorate further and fast, the Fed is signaling that it wants to save some ammo. That’s the only way it can bring maximum firepower to bear if and when it’s needed.

Besides, with the next Fed Open Market Committee meeting scheduled for July 31 and Aug.1, QE3 could still be coming none too soon.